THEORETICALLY the government has _some_ restrictions against monitoring US citizens (https://www.brennancenter.org/our-work/research-reports/soci...), and it sounds like none of those are deemed to apply if you're using a VPN, per the original article.
Many VPNs are owned and operated by organized crime, intelligence services from all kinds of nations, and cops. The idea that a VPN somehow protects you does not enjoy a rational basis.